Two secret documents describing the procedures the National Security Agency (NSA) is required to follow when spying on foreign terror suspects reveal the provisions that allow the agency to collect, retain and use information on U.S residents without a warrant, The Guardian newspaper reported today.

Both the documents are dated July 28, 2009 and are signed by Attorney General Eric Holder. They also appear to have been approved by the Foreign Intelligence Surveillance Court, a secret court that was established specifically to oversee government data access requests filed under Foreign Intelligence Surveillance Act of 1978.

FISA was originally designed to give U.S. intelligence a tool for keeping an eye on suspects in foreign countries who were perceived to pose a threat to U.S. national security. It was amended in 2008 and now gives U.S. intelligence agencies significantly broader authority to keep an eye on the communications that foreign-based suspects have with people outside the country and inside the U.S.

One document published by The Guardian describes the procedures that NSA agents need to follow when spying on people who are reasonably believed to be outside the United States. The other describes the data minimization procedures that the NSA is required to follow when gathering, retaining and using electronic communications and other information pertaining to foreign suspects.

The documents make it clear that the NSA is not permitted to intentionally conduct surveillance or intentionally collect information on U.S residents under the authority granted to it by FISA.

They also show that several detailed procedures exist to ensure that inadvertent collection of data on U.S. residents is kept to a minimum. The secret documents describe the measures the NSA must take to ensure that targets are indeed based outside the USA and how they must destroy data that is inadvertently collected on U.S. residents.

Even so, the court-approved documents also show that the NSA is allowed to retain "inadvertently acquired" data on U.S. persons for up to five years if the data contains usable intelligence, if the data is encrypted, or contains information on criminal activity, the Guardian said.

The NSA can similarly retain inadvertently collected data on U.S. residents if the data contain information relevant to cybersecurity or evidence of a threat of harm to persons or property. It also allows the NSA to access the actual content of communications inadvertently gathered from U.S. systems to establish if the systems are indeed based in the U.S. and to eliminate them from further surveillance.

In situations where the NSA does not have any information on a person's location, they are free to assume that the person is based overseas, the report noted, citing from a 2010 court order it says it has obtained.

"If it later appears that a target is in fact located in the US, analysts are permitted to look at the content of messages, or listen to phone calls, to establish if this is indeed the case," the paper said.

Such information would appear to undercut comments made by various administration and intelligence officials about the NSA's foreign surveillance activities not impacting U.S. residents. Though officials have conceded that their surveillance activities may occasionally result in information on U.S. residents being gathered, they have tended to downplay the impact of such information gathering.

The Guardian's latest revelations comes about two weeks after it first broke the story about the NSA collecting phone call metadata records pertaining to all calls made by Verizon customers since at least April. That revelation, followed by another from The Washington Post about another secret surveillance program called PRISM have resurfaced long-held fears among privacy advocates about post 9-11 anti-terror programs being used as an excuse to conduct dragnet domestic surveillance.

Two lawsuits have already been filed against the administration, the Justice Department and the NSA over the data collection programs. Several lawmakers have also asked for more transparency and oversight over the programs.

On Thursday, two lawmakers introduced a bill in the U.S. House of Representatives that would require the Department of Justice to declassify significant decisions made by the Foreign Intelligence Surveillance Court. The goal is to give Americans a chance to understand how the court has interpreted the authorities provided to the government under FISA and the Patriot Act.

Meanwhile, Snowden, the man at the center of the story, is believed to be hiding in Hong Kong and is reportedly said to be looking for asylum in Iceland. The FBI is expected to press criminal charges against him shortly.